1. Field of the Invention
The present invention is directed to a device and a corresponding method for the defined orientation of an eye for diagnostic or therapeutic purposes, wherein the line of sight need not necessarily coincide with the optical axis of the examination apparatus or treatment apparatus.
2. Description of Related Art
In ophthalmology, it is known in diagnostic or therapeutic methods to position and orient the patient's eye with a certain accuracy in relation to a device suitable for carrying out the method. The orientation and positioning of the eye in question is generally carried out on or along the optical axis of the apparatus in question.
For this purpose, the patient's head was fixed by means of a chin support and/or forehead support and the apparatus was then positioned by the operator in such a way that the patient's eye was situated so as to be approximately centered in front of the optical system of the apparatus. If the patient was lying down on a couch, for example, the couch was generally moved with the patient and oriented to the optical system of the apparatus. In every case, the detection and evaluation of the position of the eye of the patient is first carried out by the operator in that the patient's eye is observed directly via an optical or electronic observation system and is positioned corresponding to the apparatus such as an ophthalmological examination instrument or a surgical microscope.
After positioning, the orientation of the patient's eye, i.e., the orientation of its line of sight, is usually carried out by showing the patient a fixating light to which the eye is oriented. The fixating light supplied by the device is usually generated by a separate light source and is blended into the optical axis of the device so that the eye of the patient is oriented along the optical axis of the device and the fixating light is focused on the macula of the patient. According to the known prior art, continuously illuminating fixating marks as well as blinking fixating marks are used for this purpose.
In therapeutic ophthalmological devices in particular, the orientation of the patient's eye is acquired and evaluated so that any faulty orientation can be taken into account in the therapeutic treatment. In this automatic position acquisition, known as tracking, neither the patient's eye nor the fixating light is moved.
DE 102 54 369 A1 describes an ophthalmological apparatus with an eyetracker unit for measuring structures by means of variably structured illumination patterns by which eye movements can be compensated by tracking. For this purpose, the illumination pattern is moved relative to the apparatus corresponding to a detected eye movement, i.e., the illumination pattern is tracked by the eye movement and thus appears to be “connected” to the eye. The eyetracker unit which is used for detecting the eye movement is coupled with the optical axis of the observation system and delivers signals which exactly define the pupil center.
The illumination pattern is preferably generated by IR illumination so that it is only visible to the operator and not to the patient and is evaluated by a corresponding camera.
DE 103 14 944 A1 describes an illuminating and irradiating unit for ophthalmological devices for illuminating/irradiating the human eye for purposes of observation and/or treatment. The light generated by the illumination source is coupled into the observation system by devices for generating special illumination patterns such as, e.g., filters, diaphragms and/or optoelectronic light modulators and optical means such as beamsplitters, semitransparent mirrors, or the like. The illumination patterns generated in this way are projected into the patient's eye by projection optics and the objective of the ophthalmological apparatus.
Although this solution serves primarily to illuminate an eye, generated illumination patterns can be tracked by means of an eyetracker unit relative to the apparatus corresponding to a detected eye movement.
In this solution, the illumination pattern is also only visible to the operator and not to the patient and the detected eye movement is tracked.
By means of the method described in DE 103 59 239 A1 for displaying a fixating mark for ophthalmological treatment devices, unwanted eye movements of an eye to be treated are prevented or at least minimized. For this purpose, the fixating mark is projected in the field of view of the patient so that the patient orients the eye to be treated on the fixating mark by foveal focusing. In a particular construction, the fixating mark is moved in such a way that the patient can follow the movement.
However, the fixating mark can also be used for specific positioning of the eye, wherein the fixating mark is projected in the visual field of the eye to be treated so that the patient orients the eye to be treated on the fixating mark through foveal focusing. The fixating mark is then moved in such a way that the patient can follow the movement.
In contrast to the references mentioned thus far, DE 41 08 435 describes an arrangement for monitoring fixation which can preferably likewise be applied for devices for examination of the visual field, but principally also for other ophthalmological examination instruments. For this purpose, means are provided for rotating a structured fixating mark around a central axis to furnish a functional, reproducible fixation stimulus. The fixating mark has a structure and a predominant direction which can only be identified by the test subject when foveally fixated by the test subject. This is achieved in that the fixation mark is formed, for example, as a Landolt ring which adopts discrete directional orientations when rotated. A Geneva drive generates the discrete directional orientations of the fixating mark from a uniform rotating movement in 90-degree rotations with a stationary period. The test subject must constantly follow the slit of the Landolt ring during the examination, which can be accomplished only with corresponding foveal fixation.
Although the fixating mark is visible to the patient in this solution, the fixating mark cannot be used for specifically positioning the eye because, except during a brief stationary phase, the fixating mark is moved constantly and the line of sight of the eye being examined or treated accordingly changes. Further, this solution only affords the possibility for the fixating mark to appear with a certain variation (rotation) only in a predetermined direction.